What is Collagen: Types of Collagen, Genetic Diseases of Collagen
What is Collagen?
It is commonly asked, what is collagen? Collagen is found in our bones, muscles, blood vessels, digestive system, tendons, and skin. Collagen is what gives our skin its strength and elasticity and also replaces dead skin cells. It is also the 'glue' that holds our joints and tendons together. With age, the production of collagen in the body starts to decline. Due to this slow down, the body starts displaying signs of aging such as sagging skin, wrinkles, as well as joint pains.
Apart from age, lifestyle choices we make also has a big role to play in depleting the body's collagen levels. Consuming a diet rich in sugar, smoking and drinking alcohol, along with too much sun exposure can contribute to lower levels of collagen in the body. Collagen-related diseases arise from a combination of not consuming collagen-rich foods, digestive problems, nutritional deficiencies, and genetic defects. Due to the varied location of the collagen types in the body, they are generally associated with a host of diseases. Collagen-linked diseases often lead to problems in the biosynthesis of the collagen molecule in the body, issues with their assembly, and also in the post-translational modification procedure that creates the final form of collagen.
Collagen promotes healing and also provides the best platform for boosting the growth of new tissues. Collagen dressings are used to heal several injuries, necrotic wounds, burns and even for skin grafts and skin donation.
Membranes that are based on collagen are also used in various implant therapies and also in periodontal therapy for promoting the growth of cells of a specific type. Collagen supplements are also used to treat osteoarthritis and in skin revitalization.
Types of Collagen
There are 28 types of collagen that have been identified in our body to date. However, type 1 collagen makes up nearly 90 % of all collagen in the body and is the most common type of collagen in the human body.
Here are the five most common types of collagen in the body.
- Collagen I: This commonest type of collagen is the main component of the organic part of all bones in the body. It is also a component of skin, vascular ligature, tendon, and organs.
- Collagen II: This collagen is the main component of cartilage.
- Collagen III: It is the main component of all reticular fibers in the body and is generally found along with type I collagen.
- Collagen IV: This type of collagen forms the basal lamina.
- Collagen V: Collagen type V is found on cell surfaces, placenta and hair.
Genetic Diseases of Collagen
Diseases of collagen usually arise from nutritional deficiencies in the body or from genetic defects. Nutritional deficiencies affect the biosynthesis, assembly, secretion, post-translational modification, or other processes involved in the normal production of collagen. This is a common causes of diseases of collagen. Osteoporosis, one of the diseases of collagen is not a genetic disease and is caused by age. It is associated by lower levels of collagen in the skin and bones.
Genetic diseases of collagen can cause defects in not only the general production of collagen but also in collagen secretion. Researchers have identified one thousand mutations in twelve types of collagen. These mutations can give rise to various diseases of collagen like
- Alport syndrome: This condition causes problems with kidneys and eyes. Hearing loss can also develop in childhood or adolescent years. This syndrome, is one of the genetic diseases of collagen and can be passed on children.
- Chondrodysplasias: This is a skeletal disorder and it is believed to be caused by a mutation in type 2 collagen.
- Ehlers-Danlos Syndrome: There are nearly ten different types of this syndrome, which is one of the genetic diseases of collagen. This condition causes deformities in connective tissue. The syndrome is a condition characterized by stretchy skin, over-flexible joints, and an abnormal growth of scar tissue. Some types of Ehlers-Danlos syndrome can be life-threatening and lead to the rupture of arteries. Each type of this syndrome is caused by a different mutation on different collagen types.
- Knobloch Syndrome: This condition causes degeneration of the retina and can also lead to a protrusion of the brain tissue. This too is one of the rare genetic diseases of collagen.
- Osteogenesis imperfecta: This condition results in irregular connective tissue and weak bones. Osteogenesis imperfecta causes brittle bones, lax joints and ligaments, and low muscle mass. The condition is caused by a mutation in type 1 collagen. Severe cases of this disease cause structural defects in collagen.
Which Genes Get Affected By Collagen Disorder?
Let us now take a look at the role of genes to understand, which gene is affected by which collagen disorder.
Type I Collagen Disorders: Present in scar tissue and found in skin, tendons, artery walls, fibrocartilage, organic part of teeth and bones, endomysium of myofibrils, type 1 collagen is the most abundantly available collagen in the body. Genetic disorders caused by mutations in type 1 collagen include Ehlers-Danlos Syndrome, Infantile cortical hyperostosis or Caffey's disease, and osteogenesis imperfecta. These occur in the genes COL1A1 and COL1A2.
Type II Collagen Disorders: Collagenopathy is the genetic disorder that occurs from mutations caused in type II collagen. Type II collagen makes up nearly 50 percent of all cartilage protein and it is also found in the vitreous humor of the eye. The mutation occurs in the gene COL2A1.
Type III Collagen Disorders: Ehlers-Danlos Syndrome is caused by a mutation in the gene COL3A1. Type III collagen is the collagen of granulation tissue. It is produced by young fibroblasts. It is also found in skin, intestines, artery walls, and also the uterus.
Type IV Collagen Disorders: Alport syndrome and Goodpasture's syndrome is caused by a mutation in collagen type IV. Type IV collagen is found in the eye lens and also as part of the filtration system in capillaries. Mutations occur in the genes COL4A1, COL4A2, COL4A3, COL4A4, COL4A5, and COL4A6.
Type V Collagen Disorders: Mutation in type V collagen also causes Ehlers-Danlos syndrome. Genes associated with this disorder are COL5A1, COL5A2, and COL5A3. Type V collagen is found is most interstitial tissue.
Type VI Collagen Disorders: Genes associated with causing mutations in type VI collagen include COL6A1, COL6A2, and COL6A3. Conditions which arise from these mutations include Ulrich myopathy and Bethlem myopathy.
Type VII Collagen Disorders: This type of collagen forms anchoring fibrils in the dermal-epidermal junctions. The mutation occurs in the COL7A1 gene and gives rise to the conditions of epidermolysis bullosa and dystrophica.
Type VIII Collagen Disorders: This type of collagen is present in endothelial cells. Mutations of this type of collagen cause posterior polymorphous and corneal dystrophy 2. COL8A1 and COL8A2 are the genes associated with the mutations.
Type IX Collagen Disorders: Mutations occur in the genes COL9A1, COL9A2, and COL9A3. This type of collagen is present in type II and XI fibrils and also in cartilage. Conditions that arise from mutations in type IX collagen include EDM2 and EDM3.
Type X Collagen Disorders: Schmid metaphyseal and dysplasia are the conditions that arise when mutations occur in type X collagen. COL10A1 is the gene in which the mutation occurs. This type of collagen is present in mineralizing cartilage.
General Symptoms of Collagen Disorders
While each type of collagen disease has its own unique symptoms, most of them also share some general symptoms. Genetic diseases of collagen too may show these symptoms. Patients suffering from collagen disorders usually experience the following:
- Muscle weakness
- Joint and body pain
- Skin rash
- Dry eyes
- Mouth ulcers
- Shortness of breath
- Diarrhea or constipation
- Coughing or wheezing
While many people with collagen-based genetic diseases present with mild symptoms, other individuals may experience critical complications.
Treatment of Collagen Disorders
The treatment of diseases of collagen differs according to the type of condition you have. However, immunosuppressant medications and corticosteroids are generally used to treat most of types of collagen disorders. Other symptomatic treatment is also used. Physical therapy or gentle exercise is also used to treat muscle and joint related symptoms. These exercises will help you retain your mobility and also work towards reducing your body pain.
The long-term outlook of diseases of collagen varies from individual to individual. It also depends on the kind of collagen disorder. However, one thing that remains constant across all the disorders is that such autoimmune diseases are chronic conditions and have to be managed throughout your life. They have no cure and doctors usually create a treatment plan that helps to manage the symptoms. Learning how to manage the disorder and its symptoms are important in improving the quality of life.
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